1. Field of the Invention
This invention relates to relay apparatus. In particular, it relates to electromagnetically actuated switches of mercury relay apparatus.
2. Description of the Prior Art
Sealed contact switches are well known in the Electronic and Communication Industry and have found extensive application in electrical systems for performing a wide range of switching functions. A typical switch comprises contact members suspended at their ends by an envelope member such as a sealed glass envelope. A relay is constructed utilizing a switch such that a coil winding encircling the envelope member is energizable to generate a magnetic field for actuating the contact members of the switch to engage and disengage contact surfaces thereby controlling an external electrical circuit connected with the switch contact members. Such switches serve well in particular circuit applications. However, the irregular surface character of the contact members reduce the contact surface area of the electrical connection upon engagement of the contact surfaces and renders the switch essentially current limited in that current of a magnitude beyond a predetermined value tends to cause melting of the irregular contact surfaces. The melting of the contact surfaces increases the tendency of the contact members to stick together in a closed position.
The current carrying capacities of such switches may be increased by the employment of the well-known mercury-wetted type switches. Typically, mercury wettable surfaces enable an electrical connection to be uniformly established over the entire area of the contact surfaces. In such a switch, a pool of mercury located in one end of the sealed envelope member moves by capillary action over one contact member to wet both contact surfaces and thereby increase the current capacity of the switch. A problem occurs with mercury switches in that they are position sensitive. If they are mounted in one position, the pool of mercury will shift thereby shorting the contact members together rendering the switch inoperable. If the switch is mounted in another position, the pool of mercury may be shifted to a location within the switch away from the contact members thereby creating dry contacts that result in a lower current carrying capacity of the switch.
Accordingly, a need exists for a multi-positional mercury switch that may be mounted in various positions in electrical and electronic equipment. A need also exists for a mercury relay having a multi-positional switch assembly that requires less mercury to obtain the current rating of previous switch assemblies.